Touch ID refers to a biometric fingerprint authentication technology patented by Apple. With this feature enabled, iPhone users are able to use the Home button to unlock their device as well as authorize purchases on the iTunes Store.

Here are the steps for you to set up Touch ID on your iPhone SE handset:

1. Tap Settings from the Home screen to get started.

2. From the Settings menu, scroll to and tap to select Touch ID & Passcode.
3. Enter the passcode as required.

Note:
You may need to enable the passcode if necessary. If a passcode is not yet enabled, then do the following first:

Tap Turn Passcode On.

Enter your preferred passcode.

Confirm your passcode on the next screen to proceed.

4. Tap the Add a fingerprint button.

5. Position your finger or thumb on the Home key.

6. Follow the onscreen prompts to complete the Touch ID set up process.

7. After successfully setting up your Touch ID, tap Continue.

Touch ID is now set up and ready for use -- to unlock your iPhone, Apple Pay, iTunes, or App Store purchases authorization.

If you want to allow Touch ID to be used in authorizing purchases, simply tap the iTunes & App Store switch to enable the feature on your iPhone.